Combine balloons with skyhooks. https://www.youtube.com/watch?v=dqwpQarrDwk

Edit:

According to proprietary imtringued numbers the hydrogen for a balloon capable of lifting 1kg to 50km would be $800 if you do not reuse the hydrogen. The skyhook would accept vehicles at an altitude of 100km so no, keep balloons out of the space launch industry.